The Second Battle of Fallujah, initially codenamed Operation Phantom Fury, Operation al-Fajr was an American-led offensive of the Iraq War that lasted roughly six weeks, starting 7 November 2004. Marking the highest point of the conflict against the Iraqi insurgency, it was a joint military effort carried out by the United States, the Iraqi Interim Government, and the United Kingdom. Within the city of Fallujah, the coalition was led by the U.S. Marine Corps and U.S. Army, the battle was later described as "some of the heaviest urban combat Marines have been involved in since Huế City in Vietnam in 1968" and as the toughest battle the U.S. military has been in since the end of the Vietnam War. It was the single bloodiest and fiercest battle of the entire conflict, including for American troops.

The 1st Marine Regiment is an infantry regiment of the United States Marine Corps based at Marine Corps Base Camp Pendleton, California. The regiment is under the command of the 1st Marine Division and the I Marine Expeditionary Force. The 1st Marine Regiment is also sometimes referred to as "Regimental Combat Team 1" or "Inchon".